02 cr250 piston and size


9 replies to this topic
  • stephen99

Posted December 27, 2011 - 06:53 AM

#1

hi there i want to rebuild the topend in my bike. is there anyway to find out what size piston i need rather than taking it to honda and getting robbed. i can see them charging me to measure the cylinder. and then charging me 200 dollars for a oem honda crap piston. and i dont wanna buy some crazy tool to measure it myself that i dont know how to use. is there any markings on the piston that will help me. maybe i just have to get robbed by celigh honda like i have many times. the last time i went there they charged me 60 dollars for brake pads that barly lasted 1 mounth. does anyone have any advice that may help me. ... no smart ass comments please. thanks guys cheers!

  • RedRider501

Posted December 27, 2011 - 07:35 AM

#2

If you have not had the cylinder bored out and a bigger than stock piston put in, there should be an "A" or "B" stamped somewhere on the piston. One is slightly larger than the other. Usually when ordering a new piston you can pick between an A or B size. This is the way my CR125 was when I done the topend in it. Im assuming the 250 is the same.

  • pieplatesnductape

Posted December 27, 2011 - 07:45 AM

#3

for Honda pistons, your Jug will have "A" or "B" stamped near the base. Wiseco will work with either.
If your bike is used, and you don't know what condition the cylinder is in, it should be measured before installing a new piston.

  • JJRace

Posted December 27, 2011 - 08:20 AM

#4

If you want it to last then you MEASURE THE BORE! that is how to determine the size of the piston. Take it to your local dealer and ask them to measure the bore for you.

also if the bore is not round, you will need to fix that. you also check that while measuring the bore.

if you want to guess go for it. But expect problems if you guess wrong.

  • CamP

Posted December 27, 2011 - 08:27 AM

#5

Honda only sells the B piston for the '02. You can buy one for $56 here. http://www.cyclecent...=2002&fveh=3273

  • ca_101

Posted December 28, 2011 - 06:33 AM

#6

First step- Take it to a auto or motorcycle machine shop and have them measure the bore of the cylinder. They will do it a lot cheaper than the Honda dealer. Basically, just find any shop that bores cylinders and they will be able to give you the measurements you need.

You can figure out which piston you need after that.

  • hardhitwarrior

Posted December 28, 2011 - 06:56 AM

#7

if it says A or B then you are safe to use A or B. nikasil doesnt wear out thta much if yiou dont see any aluminum thru it.

iv never had an issue getting the size same as the cylinder. or measure the old piston (assuming it ran well b4) and buy thesame size or maybe, 0.01mm more.

  • stephen99

Posted December 28, 2011 - 01:36 PM

#8

yea thanks . i think ill take it to engine tech 2000 and have it measured is the best thing because i bought the bike used and dont know much of its history. cheers!

  • hardhitwarrior

Posted December 28, 2011 - 06:09 PM

#9

this is how yu should do it. my opinion only.

inspect your cylinder for wear and marks that is big enough that might catch your nail.

if cylinder is good looking then id look at the left side-rear bolt location where it will be stamped an A or B.

you can also look under the cylinder just under the part of where the reed cage would be (but outside of it). there will also be an A or B.

then follow that size with the piston purchase.

if you go cast. you may use A or B on on that "A" cylinder. if the cylinder is a "B" then use a B or C (might work with a D size) piston.

if you go forged: id suggest to use the corresponding size according to cylinder letter. that way youll have good clearance for the forged piston`s repid expansion.

Edited by hardhitwarrior, December 28, 2011 - 06:10 PM.
too much wrong spelling _:)


  • stephen99

Posted December 29, 2011 - 06:32 AM

#10

this is how yu should do it. my opinion only.

inspect your cylinder for wear and marks that is big enough that might catch your nail.

if cylinder is good looking then id look at the left side-rear bolt location where it will be stamped an A or B.

you can also look under the cylinder just under the part of where the reed cage would be (but outside of it). there will also be an A or B.

then follow that size with the piston purchase.

if you go cast. you may use A or B on on that "A" cylinder. if the cylinder is a "B" then use a B or C (might work with a D size) piston.

if you go forged: id suggest to use the corresponding size according to cylinder letter. that way youll have good clearance for the forged piston`s repid expansion.

kool thanks





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